Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$144.85	12.623%	$163.1344	$163.13	$163.15	$163.10
Purchase #2	$52.98	7.821%	$57.1236	$57.12	$57.10	$57.10
Purchase #3	$112.42	3.576%	$116.4401	$116.44	$116.45	$116.40
Purchase #4	$51.48	8.625%	$55.9202	$55.92	$55.90	$55.90
Purchase #5	$40.94	11.239%	$45.5412	$45.54	$45.55	$45.50
Purchase #6	$70.41	13.627%	$80.0048	$80.00	$80.00	$80.00
Purchase #7	$53.38	4.661%	$55.868	$55.87	$55.85	$55.90
7 purchase totals =	$526.46		$574.0323	$574.02	$574.00	$573.90